<template>
  <div class="music-list" ref="musicList">
    <div class="back" @click="back"><i class="icon-back"></i></div>
    <h1 class="title" v-html="title"></h1>
    <div class="bg-title" ref="bgTitle"></div>
    <div class="bg-image" :style="bgStyle" ref="bgImage">
      <div class="play-wrapper">
        <div class="play" v-show="songs.length>0" ref="play" @click="random">
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
    </div>
    <div class="bg-layer" ref="layer"></div>
    <scroll :probe-type="probeType" :listen-scroll="listenScroll" @scroll="scroll" :data="songs" class="list" ref="list">
      <div class="song-list-wrapper">
        <song-list :rank="rank" :songs="songs" @select="selectItem"></song-list>
      </div>
      <div class="loading-wrapper" v-show="!songs.length>0">
        <loading></loading>
      </div>
    </scroll>
  </div>
</template>

<script>
import SongList from 'base/song-list/song-list'
import Scroll from 'base/scroll/scroll'
import {prefixStyle} from 'common/js/dom'
import Loading from 'base/loading/loading'
import {mapActions} from 'vuex'
import {playlistMixin} from 'common/js/mixin'

const RESERVED_HEIGHT = 40 // 预留顶部空间40px
const transform = prefixStyle('transform')
const filter = prefixStyle('filter')

export default {
  name: 'music-list',
  props: {
    bgImage: {
      type: String,
      default: ''
    },
    songs: {
      type: Array,
      default: () => []
    },
    title: {
      type: String,
      default: ''
    },
    rank: {
      type: Boolean,
      default: false
    }
  },
  created () {
    this.probeType = 3
    this.listenScroll = true
  },
  data () {
    return {
      scrollY: 0
    }
  },
  computed: {
    bgStyle () {
      return `background-image: url(${this.bgImage})`
    }
  },
  components: {Scroll, SongList, Loading},
  mounted () {
    this.imageHeight = this.$refs.bgImage.clientHeight
    this.minTransY = -this.imageHeight + RESERVED_HEIGHT
    this.$refs.list.$el.style.top = `${this.imageHeight}px`
  },
  mixins: [playlistMixin],
  methods: {
    handlePlaylist (playlist) {
      const bottom = playlist.length > 0 ? '60px' : ''
      this.$refs.list.$el.style.bottom = bottom
      this.$refs.list.refresh()
    },
    scroll (pos) {
      this.scrollY = pos.y
    },
    back () {
      this.$router.back()
    },
    ...mapActions([
      'selectPlay',
      'randomPlay'
    ]),
    selectItem (item, index) {
      this.selectPlay({
        list: this.songs,
        index
      })
    },
    random () {
      this.randomPlay({
        list: this.songs
      })
    }
  },
  watch: {
    scrollY (newVal) {
      let transY = Math.max(newVal, this.minTransY)
      let scale = 1.0
      let zIndex = 0
      let blur = 0
      // 往下拉动列表
      const percent = Math.abs(newVal / this.imageHeight)
      if (newVal > 0) {
        scale = 1 + percent
        zIndex = 10
      } else {
        blur += Math.min(8, percent * 8)
      }
      this.$refs.bgImage.style[filter] = `blur(${blur}px)` // 图像模糊
      this.$refs.bgImage.style[transform] = `scale(${scale})`
      this.$refs.layer.style[transform] = `translate3d(0,${transY}px,0)`
      if (newVal < this.minTransY) {
        zIndex = 10
        this.$refs.bgImage.style.paddingTop = 0
        this.$refs.bgImage.style.height = `${RESERVED_HEIGHT}px`
        this.$refs.bgTitle.style.opacity = '1.0'
        this.$refs.play.style.display = 'none'
      } else {
        this.$refs.bgImage.style.paddingTop = '70%'
        this.$refs.bgImage.style.height = 0
        this.$refs.bgTitle.style.opacity = 0
        this.$refs.play.style.display = 'block'
      }
      this.$refs.bgImage.style.zIndex = zIndex
    }
  }
}
</script>

<style lang="less" scoped>
  @import '~common/css/variable';
  @import '~common/css/mixin';
  .music-list {
    position: fixed;
    z-index: 100;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: @color-background;
    .back {
      position: absolute;
      top: 0;
      left: 6px;
      z-index: 50;
      .icon-back {
        display: block;
        padding: 10px;
        font-size: @font-size-large-x;
        color: @color-theme;
      }
    }
    .title {
      position: absolute;
      top: 0;
      left: 10%;
      z-index: 40;
      width: 80%;
      .no-wrap;
      text-align: center;
      line-height: 40px;
      font-size: @font-size-large;
      color: @color-text;
    }
    .bg-title{
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 40px;
      background: @color-background;
      opacity: 0;
      z-index: 9;
    }
    .bg-image {
      position: relative;
      width: 100%;
      height: 0;
      padding-top: 70%;
      background-size: cover;
      transform-origin: top;
      .play-wrapper {
        position: absolute;
        bottom: 20px;
        z-index: 50;
        width: 100%;
        .play {
          box-sizing: border-box;
          width: 135px;
          padding: 7px 0;
          margin: 0 auto;
          text-align: center;
          border: 1px solid @color-theme;
          border-radius: 100px;
          font-size: 0;
          .icon-play {
            display: inline-block;
            vertical-align: middle;
            margin-right: 6px;
            font-size: @font-size-medium-x;
          }
          .text {
            display: inline-block;
            vertical-align: middle;
            font-size: @font-size-small;
          }
        }
      }
    }
    .bg-layer{
      position: relative;
      background-color: @color-background;
      width: 100%;
      height: 100%;
    }
    .list {
      position: fixed;
      top: 0;
      bottom: 0;
      width: 100%;
      background: @color-background;
      .song-list-wrapper{
        padding: 20px 30px;
      }
      .loading-container {
        position: absolute;
        width: 100%;
        top: 50%;
        transform: translateY(-50%);
      }
    }
  }
</style>
